In order to investigate the physiological characteristics of different uniform strains of mice in Japan, stains of DDN, SM, CF # 1 and CFW mice, each comprising of 20 or 21 were tested. About one half of each strain mice was used as the CS2 group and the other half as the control group. The CS2 group was exposed to 500ppm CS2 of 8 hours a day except sunday for 30 days. The body weight was measured three times during this period, and hemoglobin content and leucocyte counts were determined at the

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... end of this exposure. Immediately after these examinations, the secondary exposure of CS2 in a higher concentration of 1500ppm was made to both groups. From which the death rates of mice by the gas were calculated. The results obtained were as follows: 1. By the secondary exposure of CS2 gas in 1500ppm, the death rate showed remarkably larger in the CS2 group than in the control, and the difference between strains or sexes in the same strain was recognized to be significant. 2. The increase of body weight in the CS2 group was slightly smaller than in the control. The variation in hemoglobin contents was small, but the leucocyte count in CF # 1 or CFW was increased significantly by the exposure. 3. There was a little effect of toxicity of CS2 on mice by repeated exposures in a small concentration. But the death rate of the repeatedly exposed group after inhaling a larger concentration of CS2 was far greater than that of the contral group, in which only a few deaths were seen. This fact may provide for an experimental method for detecting the inapparent toxic effect of industrial poisons.